Over the last couple of decades it’s become easier to recycle almost everything. But even if you’re fastidious about sorting your paper, cans, and bottles, you might not have thought too much about what happens to them or other recyclable products once they leave your hands. You can probably imagine without too much trouble what happens to some of them, such as those made of glass or metal, but others might be more difficult to picture.

Take, for example, printer ink cartridges. If you own an inkjet printer, you're undoubtedly aware of how many you go through, and thus what's necessary to dispose of them. Sure, you can just throw them away, but there are potentially more attractive options for both you and the environment. An increasing number of wholesale and office supply stores are providing ways for you to return your empty cartridges to both help out the environment and get in-store discounts. But once you turn over your cartridge, isn’t the process of turning it into another one probably pretty complex?

I recently received a first-hand opportunity to answer this question, courtesy of one of the biggest printer and ink manufacturers in the computer market: HP. Representatives from the company invited PCMag to tour the biggest of its global recycling plants, located in Smyrna, Tennessee (a suburb of Nashville), which is responsible for tearing down empty ink cartridges into the component pieces that can then be used to construct new ones. And it was a fascinating education into one ubiquitous tech company solves a problem most of us don’t think about.

My tour of the 80,000-square-foot plant, which opened in 2001 and received a major expansion in 2009, revealed the three stages through which cartridges pass as they're de-transformed into useful raw materials again. Though humans are involved at every step along the line, most of what happens is highly automated—and because these techniques are proprietary, there's a lot of information my tour guide, Plant Manager Jeff Wirick, wouldn't give me, and I was only allowed to take a limited number of photos. (You can see my approved snapshots in the slideshow.)

But the workflow for the plant looks something like this:

1. Receiving. The logical first step is for HP to actually get the cartridges in house from the various places (such as Staples) that operate on the front lines of the recycling push. Enormous boxes full of sealed envelopes containing anywhere from three to 20 cartridges are located around the receiving area. The senders, however, do not perform any more advanced sorting on the cartridges. HP takes care of all of that here—in fact, it's where the cartridges go next.

2. Sorting. Though in certain circumstances some sorting of the cartridges is done by the people working in receiving, most can be done via elaborate automatic or semi-manual methods. The semi-manual method is used for certain types of cartridges that arrive encased in bags within boxes; the boxes need to be open and the cartridges loaded into a device that splits open the bags to release the contents. (Only about five percent of all cartridges need to be handled in this way.) All eligible cartridges from there, and from the rest of the receiving process, go directly to the automatic sorting machine, which we got to spend some quality time with. Wirick told me it is capable of sorting “tens of thousands an hour” (because the volume can be tied to sales, Wirick said, exact numbers are again hush-hush) of 20 different kinds of cartridges. Cartridges are moved from the receiving area and loaded by the hundreds into a sorting machine that uses a system of four separate conveyor belts to nudge the units into a single-file line. Finally, each cartridge in the lengthy procession is analyzed by a laser and camera to determine its precise make and model, and is blown by a powerful puff of air off the belt and into the appropriate bin to be taken apart. Our guide estimated the automated sorting machine has an accuracy rate of 95 percent.

3. Recycling. Because of the large number of types of ink cartridges HP deals with, a number of different methods are required for taking them apart. In this case, there are three. The “old-fashioned” way, and the certainly the most brute-force of them, is shredding, which is exactly what it sounds like: The cartridges meeting the proper criteria (many smaller ones, often made of polypropylene, or PP) are dumped from one of those bins onto a conveyer, which mechanically separates them and then rips them apart. More complex cartridges (including many constructed from polyethylene terephthalate, or PET) proceed through the newer (as of the last couple of years) and more complicated disassembly process, which HP says recovers 50 percent more plastic than the shredding route. The units are fed by the dozens into a machine that knocks off the cap, pulls out the empty ink-containing foam inside, removes the other in-the-way internals, and then drops the empty plastic hull in a box for easy transport. While I was watching the machine chug away, I noticed that quite a few units (or “bodies”) made it to the end of gauntlet with their internal foam intact and in place; even though the machine hadn't been able to completely disassemble them, but it was capable of determining something had gone wrong and redirect these cartridges to a separate container so they could be fed back into the machine for one more go-around. Owing to their more unusual, oblong-shaped design and large labels, some cartridges can’t go through this disassembly procedure. So they’re “demanufactured”: A worker applies a powerful adhesive to a box of cartridges then loads it into a machine that pulls off the top and side of each one, pushes out the ink envelope it contains, and sends the rest of the body on its way.

After the cartridges have been received, sorted, recycled, and shredded, the resulting pieces are rinsed and cleaned before they're transported to Montreal. There, the company Lavergne combines them with local recycled plastic from other sources such as used drinking water bottles, or Virgin plastic in the case of larger LaserJet toner cartridges (which, for the most part, HP does not process at the Smyrna facility I visited), and additional plastic additives to create new cartridges that HP claims are every bit as good as the originals. (Okay, one of our contacts actually said they were even better than the originals, but we’re just a bit skeptical about that.) HP customers then return those cartridges once they’ve been used up, and... Well, you get the idea.

Although it seems unlikely on the face of it, HP representatives insist that even factoring in the transportation costs their recycling program has a lesser environmental footprint than creating entirely new cartridges. Because none of the cartridge parts is discarded along the way, HP calls this its “Closed-Loop” recycling system. HP estimates that since the instigation of the HP Planet Partners program in 1991, when outside companies (such as Staples and others) in more than 50 countries and territories teamed up with HP to provide easy-to-find outlets for recycling cartridges. No cartridges or parts from them that are returned as part of this program end up in landfills, but if HP's estimates about its numbers are correct they do have an impact: Some 446 million ink cartridges have been returned, and that more than 2 billion new cartridges have been created from closed-loop recycled content. HP also estimates that, in 2011 alone, 28.6 million pounds of recycled plastic were used in new ink cartridges.

HP is already planning on incorporating an autofeed system for its disassembly machines, new separation technology for use in the closed-loop PP program, and metal hydride lights in the plant to reduce overall energy usage by 82 percent. (Skylights already reduce the need for some electricity-based lighting, at least during the daytime hours—the plant runs 24 hours a day.)

About the Author

Matthew Murray got his humble start leading a technology-sensitive life in elementary school, where he struggled to satisfy his ravenous hunger for computers, computer games, and writing book reports in Integer BASIC. He earned his B.A. in Dramatic Writing at Western Washington University, where he also minored in Web design and German. He has been... See Full Bio

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